The use of bulb-type (compact) fluorescent lamps is increasing, as these lamps have a longer life expectancy and are more efficient than incandescent light bulbs, while being usable directly in sockets for incandescent light bulbs. Bulb-type LED lamps, which are easily made compact and have a life expectancy and efficiency superior even to bulb-type fluorescent lamps, have also become available. To permit replacement of incandescent light bulbs, such bulb-type lamps are provided with the same sort of base as incandescent light bulbs.
Bulb-type fluorescent lamps have been commercialized as a replacement for incandescent light bulbs, specifically for silica bulbs having an E26 base.
There is also a desire for a replacement light source to be developed for small light bulbs, of which mini krypton bulbs are representative. Mini krypton bulbs are smaller incandescent light bulbs than silica bulbs and have an E17 base. Due to constraints on size, however, it is difficult for a fluorescent bulb to achieve the desired brightness, and therefore use of LEDs is under study.
Current lighting fixtures that use mini krypton bulbs are typically downlights, and in at least 90% of these downlights, the bulb is inserted horizontally (i.e. so that the axis of the base is orthogonal to the vertical axis) or at a nearly horizontal inclination.
By contrast, typical bulb-type LED lamps (Patent Literature 1) are provided with an LED module that is a light-emitting module for shining light primarily in a forward direction along the axis of the base. Therefore, bulb-type LED lamps are not appropriate for the above downlight fixtures.